On elementary symmetric functions of the eigenvalues of the sum and product of normal matrices Jorma Kaarlo Merikoski; Ari Virtanen — 1992 Czechoslovak Mathematical Journal
Interdependence of some problems arising in generalizing the Marcus-de Oliveira determinantal conjecture Merikoski, J.K.; Virtanen, Ari; Bebiano, Natália; Providência, João da — 1993 Portugaliae mathematica